What happened last weekend — the series of shootings that left four dead and 19 wounded in a frightening echo of Chicago’s present and New York’s past — could be a portent of worse times to come, or just an anomaly. We won’t know for a while; the safer bet is on “anomaly.”

But there are other, arguably more troubling, signs over the past year of civic reversal in New York City.

The weekend’s shootings are major crimes. The good news is that, at least so far this year, major crimes remain a relative rarity in the city — they’re down 2 percent from this time last year, which was the lowest rate on record.

Compared to the year 1990, serious crime was down — this is not a misprint — 79 percent in 2013.

The more troubling signs have to do with the kinds of issues that go under the rubric of “quality of life” and whether we’re seeing early indications of a change in the city’s general lawfulness.

That lawfulness was hard-won by the brilliant policing of the Giuliani administration in the teeth of a liberal civic culture that disrespected and actively fought against policies that led to the salvation of literally thousands of lives.

And it all started with an approach against small-bore crimes that were making the quality of life in the city far, far worse — turnstile jumpers, aggressive vagrants, squeegee men.

In their world-changing article of 1982, “Broken Windows,” George Kelling and James Q. Wilson put it this way:

Mayor Bill de BlasioPhoto: AP

“The citizen who fears the ill-smelling drunk, the rowdy teenager or the importuning beggar is not merely expressing his distaste for unseemly behavior; he is also giving voice to a bit of folk wisdom that happens to be a correct generalization — namely, that serious street crime flourishes in areas in which disorderly behavior goes unchecked. The unchecked panhandler is, in effect, the first broken window.”

The first broken windows are showing up.

Item: Saturday night, Broadway and 86th Street, Upper West Side, one of the most heavily trafficked places in a residential Manhattan neighborhood. Each of its four corners featured a panhandler — one in front of a bank, one outside a subway entrance, one at a bus stop and one next to a newsstand.

I’ve been living a few blocks away for 10 years; there has often been someone playing doorman at the bank asking for change, but never on the other corners. The panhandlers weren’t violent, but they were unpleasant.

Item: The NYPD has made 511 panhandling arrests on the subways since the start of the year, a three-fold increase over 2013.

Subway riders know from daily experience this is not due to more cops searching for people to arrest. More aggressive efforts at personal fundraising on subway cars and more people sleeping on subway platforms became a feature of the city’s system sometime in the middle of last year.

Graffiti on a subway car, New York City, New York in 1972.Photo: Everett Collection

Item: And speaking of literal “broken windows,” the Web site West Side Rag reported on June 20: “In the past 28 days, 17 cars have been broken into on Riverside Drive above 86th street . . . Fourteen break-ins have also occurred on Central Park West in the past 28 days.”

Car break-ins were a key feature of New York City in the late 1980s, as crack addicts and organized Mafiosi alike ransacked automobiles for stereos that could be fenced and sold in other countries.

These examples come from my neighborhood, which also happens to be the one where I was born and raised. The historical comparison is startling: The Upper West Side was then terrifically unsafe, but now it is an urban playground.

The subways were then a filthy and nightmarish horror show; they’re now well-managed and as clean as a system with 1.7 billion individual rides a year can be.

It’s hard to imagine that these gains can be reversed. But of course they can. New York City was as safe in 1962 as it is today; it went downhill at vertiginous speed due to changes in policy.

Policy changes have been under way since last summer. A court reined in the NYPD; Bill de Blasio ran for mayor describing the two-decade crime drop as “the stop-and-frisk era” he was going to “end.”

Are we now in a new era? If so, it might be time to get The Club for your car again, and stop carrying cash.